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Title: Earthquake Initiation From Laboratory Observations and Implications for Foreshocks
Abstract This paper reviews laboratory observations of earthquake initiation and describes new experiments on a 3‐m rock sample where the nucleation process is imaged in detail. Many of the laboratory observations are consistent with previous work that showed a slow and smoothly accelerating earthquake nucleation process that expands to a critical nucleation length scaleLc, before it rapidly accelerates to dynamic fault rupture. The experiments also highlight complexities not currently considered by most theoretical and numerical models. This includes a loading rate dependency where a “kick” above steady state produces smaller and more abrupt initiation. Heterogeneity of fault strength also causes abrupt initiation when creep fronts coalesce on a stuck patch that is somewhat stronger than the surrounding fault. Taken together, these two mechanisms suggest a rate‐dependent “cascade up” model for earthquake initiation. This model simultaneously accounts for foreshocks that are a by‐product of a larger nucleation process and similarities between initialPwave signatures of small and large earthquakes. A diversity of nucleation conditions are expected in the Earth's crust, ranging from slip limited environments withLc< 1 m, to ignition‐limited environments withLc> 10 km. In the latter case,Lcfails to fully characterize the initiation process since earthquakes nucleate not because a slipping patch reaches a critical length but because fault slip rate exceeds a critical power density needed to ignite dynamic rupture.  more » « less
Award ID(s):
1645163
PAR ID:
10443418
Author(s) / Creator(s):
 
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Solid Earth
Volume:
124
Issue:
12
ISSN:
2169-9313
Page Range / eLocation ID:
p. 12882-12904
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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